KR20020060726A - Polycarbonate Substrates - Google Patents

Abstract

The present invention relates to the production of polycarbonate substrates prepared on the basis of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, and in particular molded articles having high purity and very high surface gloss. It relates to their use in. The present invention also relates to a molded article produced from the polycarbonate substrate.

Description

Polycarbonate Substrates

The present invention relates to polycarbonate substrates prepared on the basis of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone, and in particular to molded articles having high purity and very high surface gloss. It relates to their use for production and to molded articles which can be produced with the polycarbonate substrate.

High purity polycarbonate is required for certain molded articles, in particular in molded articles that are free from defects and where high light transmission is very important, such as automotive windshields and headlight diffusers for automotive reflectors.

Polycarbonate is a so-called phase interface process in which dihydroxydiarylalkanes in the form of alkali metal salts react with phosgene in a heterogeneous phase in the presence of an inorganic base such as sodium hydroxide solution and an organic solvent in which the resulting polycarbonate is readily dissolved. phase boundary process). During the reaction, the aqueous phase is dispersed in the organic phase, and the organic phase containing the polycarbonate is washed with an aqueous solution after the reaction, in particular to remove the electrolyte, and then the washing solution is separated and removed.

Japanese patent application JP-A-07 19 67 83 discloses a process for producing polycarbonate, in which the iron content in the sodium hydroxide solution used must be less than 2 ppm in order to achieve the desired color properties.

It is an object of the present invention to provide polycarbonate molded articles having improved production alternatives and especially high purity of pure polycarbonate substrates.

Surprisingly, it has now been found that polycarbonate molded articles with particularly high surface gloss and purity can be obtained from polycarbonate substrates, the process for which the 1,1-bis- (4 having an average molecular weight of 25,000 to 400,000 produced by certain methods -Hydroxyphenyl) -3,3,5-trimethylcyclohexane.

Thus, the present invention provides 250 defects per m ² as measured by a 200 μm extruded film prepared on the basis of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone. Less than, in particular less than 150 polycarbonate substrates are provided.

The present invention also measures the number of defects per m ² as measured by a 200 μm extruded film, prepared on the basis of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone. Less than, in particular less than 150 molded articles and films, in particular automotive windshields and headlight diffusers for automotive reflectors.

Polycarbonate substrates according to the invention are obtained using a particular method.

Accordingly, the present invention relates to a polyhydroxy by phase interfacial process, wherein a dihydroxydiarylalkane in the form of an alkali metal salt reacts with phosgene in a heterogeneous phase in the presence of a sodium hydroxide solution and an organic solvent, characterized by the following a) to c). Provided are methods for preparing carbonates.

a) the raw material has a low content of Fe, Cr, Ni, Zn, Ca, Mg, Al metals or their homologues,

b) the organic solvent is separated and removed,

c) The polycarbonate obtained is worked up.

The low content of the metals or their chemical homologues in the context of the present invention means that the raw material is preferably at most 2 ppm, more preferably at most 1 ppm, particularly preferably of the entire metal, in particular of the metals and their homologues. It is meant to contain 0.5 ppm or less, most preferably 0.2 ppm or less. This limit does not apply to alkali metals.

The sodium hydroxide solution as a raw material should preferably have a low content of the metal. In particular, for NaOH content at a concentration of 100% by weight, the sodium hydroxide solution should contain not more than 1 ppm, preferably not more than 0.5 ppm, more preferably not more than 0.3 ppm of alkaline earth metals or homologues thereof. In particular, the sodium hydroxide solution as a raw material should contain 1 ppm or less, preferably 0.5 ppm or less, more preferably 0.1 ppm or less of iron, with respect to 100% by weight of NaOH content.

Sodium hydroxide solution is preferably used in the process according to the invention as a solution at a concentration of 20 to 55% by weight, particularly preferably at a concentration of 30 to 50% by weight.

Sodium hydroxide solution having the above limits can be obtained by a membrane process known in the literature.

In a preferred embodiment, apart from the sodium hydroxide solution, bisphenols, in particular bisphenols and water, particularly preferably bisphenols, water and organic solvents, are selected from metals, in particular Fe, Cr, Ni, Zn, Ca, Mg, Al. Low content

Also included in the present invention are embodiments in which sodium bisphenolate (solution) is previously prepared from sodium hydroxide solution and bisphenol (s).

The raw materials having a low metal content are obtained by distilling the solvent in a preferred embodiment, crystallizing, preferably crystallizing or distilling the bisphenol several times and using complete deionized water.

Completely deionized water is preferably desalted, degassed and / or desilierated. For example, electrical conductivity (sum parameter for ion generating substances of salts still present in traces in water) is used as a measure of quality and in the process according to the invention complete deionized water is 0.2 μS / cm (DIN 38404 C 8 Electrical conductivity below) and SiO ₂ concentration below 0.02 mg / kg (VGB 3.3.1.1).

The dissolved oxygen concentration in complete deionized water is preferably less than 1 ppm, more preferably less than 100 ppb.

In another preferred embodiment, in the group of raw materials, at least sodium hydroxide solution, preferably sodium hydroxide solution and bisphenol, particularly preferably sodium hydroxide solution, bisphenol and water, most preferably sodium hydroxide solution, bisphenol, water and The organic solvent is filtered at least once, preferably twice, most preferably three times in advance of the start of the reaction.

The present invention also relates to a polycarbonate by a phase interfacial process in which dihydroxydiarylalkanes in the form of alkali metal salts characterized by the following a) to e) react with phosgene in a heterogeneous phase in the presence of a sodium hydroxide solution and an organic solvent. It provides a method for producing.

a) the raw material has a low content of Fe, Cr, Ni, Zn, Ca, Mg, Al metals or their homologues,

b) separating and removing the organic solvent,

c) working up the obtained polycarbonate,

d) separating and removing the aqueous phase produced during the reaction, washing the separated organic polycarbonate phase with an aqueous solution,

e) The washed and separated organic polycarbonate phase from the wash liquor is optionally filtered and then heated and filtered at least once in a hot state.

In a preferred embodiment, the reaction mixture in process step d) is directly filtered after the reaction and / or the organic polycarbonate phase obtained and separated is filtered and / or the organic polycarbonate phase obtained in process step e) is filtered.

Preferably at least two of said filtrations, in particular all three, are carried out.

In a preferred embodiment, especially in the case of hot filtration, the mixture is filtered at least once, preferably twice, particularly preferably three times, in particular in stages. For staged filtration, a coarse filter is first used and then replaced by a fine filter. Preference is given to performing with a filter which has undergone filtration of the biphasic medium of process step d).

In process step e), a filter with small pore size is used for hot filtration. In this case, it is important that the polycarbonate phase be present as the most homogeneous solution. This is generally accomplished by heating an organic polycarbonate phase that still contains the residue of the aqueous wash liquor. The wash is then dissolved to form a clear solution. Pre-dissolved impurities, in particular dissolved alkali metal salts, can precipitate out and be filtered off.

In order to obtain a homogeneous solution, a freezing out process known in addition to the above-mentioned methods can be used.

To carry out filtration according to the invention, membrane filters and sintered metal filters or bag filters can be used as filters. The pore size of the filter is generally from 0.01 to 5 μm, preferably from 0.02 to 1.5 μm, more preferably from about 0.05 to 1.0 μm. Filters of this kind are available, for example, from Palsa (De-63363 Drei-Eich, Germany) and Krebsboege GmbH (De-42477 Radeborgwald, Germany; type SIKA-R CU1AS). .

The combination makes it possible to achieve a greatly improved filter life in the process according to the invention.

It is generally known to carry out other process steps. For example, the aqueous phase is emulsified during the reaction. Droplets of various sizes are produced. After the reaction, the organic phase containing the polycarbonate is generally washed several times with an aqueous solution and separated as much as possible from the aqueous phase after each washing operation. The washing is preferably carried out with very finely filtered water having a low metal content. The polymer solution is generally cloudy after washing and separation of the wash liquor. The wash solution used is an aqueous solution, dilute inorganic acids such as HCl or H ₃ PO ₄ are used to separate the catalyst, and complete demineralized water is used for further purification. The concentration of HCl or H ₃ PO _{4 in} the wash may be, for example, 0.5 to 1.0% by weight. The organic phase is preferably washed five times, for example.

Phase separation devices that can be used to separate and remove the wash liquor from the organic phase are generally known separation vessels, phase separators, centrifuges or agglomerators, or combinations of these devices.

The solvent is evaporated off to obtain a high purity polycarbonate. Evaporation can be carried out in several evaporator stages. According to a more preferred aspect of the invention, the solvent or part of the solvent is removed by spray drying. High purity polycarbonate is then obtained as a powder. The same applies to obtaining high purity polycarbonates by precipitation from organic solutions and removal of residues by drying. Extrusion, for example, is a suitable means for evaporating residual solvent. Another means is strand evaporation techniques.

1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone and 2,2-bis- (4-hydroxyphenyl) -propane (BPA / bisphenol A), optionally these Is used as bisphenol, and 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone is always present in an amount of at least 0.1 mol%. The concentration of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone is preferably in the range of 10 to 100 mol%. The bisphenol compounds used according to the invention react with carbonate compounds, in particular phosgene.

Polyester carbonates are obtained by reacting the aforementioned bisphenols with one or more aromatic dicarboxylic acids and optionally carbonic acid. Suitable aromatic dicarboxylic acids are for example orthophthalic acid, terephthalic acid, isophthalic acid, 3,3'- or 4,4'-diphenyldicarboxylic acid and benzophenonedicarboxylic acid.

Inert organic solvents used in the process according to the invention are, for example, dichloromethane, various dichloroethane and chloropropane compounds, chlorobenzene and chlorotoluene, dichloromethane and mixtures of dichloromethane and chlorobenzene are preferably used.

The reaction can be promoted by a catalyst such as tertiary amine, N-alkylpiperidine or onium salt. Tributylamine, triethylamine and N-ethylpiperidine are preferably used. Monofunctional phenols such as phenol, cumylphenol, p-tert-butylphenol or 4- (1,1,3,3-tetramethylbutyl) -phenol can be used as chain terminators and molecular weight regulators. For example, isatin-biscresol may be used as a branching agent.

In order to produce high purity polycarbonates, bisphenols are dissolved in an aqueous alkaline phase, preferably sodium hydroxide solution. The chain terminators optionally required for the preparation of the copolycarbonates are dissolved in an amount of 1.0 to 20.0 mol% relative to 1 mol of bisphenol in the aqueous alkali phase, added to the aqueous alkali phase by itself or dissolved in an inert organic phase. The phosgene is then passed through a mixer containing the remainder of the reaction components and the polymerization reaction is carried out.

Chain terminators optionally used are monophenols and monocarboxylic acids. Suitable monophenols are phenol itself, alkyl phenols such as cresol, p-tert-butylphenol, p-cumylphenol, pn-octylphenol, p-iso-octylphenol, pn-nonylphenol and p-iso-nonylphenol, Halophenols such as p-chlorophenol, 2,4-dichlorophenol, p-bromophenol and 2,4,6-tribromophenol, and mixtures thereof.

Suitable monocarboxylic acids are benzoic acid, alkylbenzoic acid and halobenzoic acid.

Preferred chain terminators are phenols of formula (I)

Food,

R is hydrogen, tert-butyl or branched or unbranched C ₈ -and / or C ₉ -alkyl radicals.

Preferred chain terminators are phenol and p-tert-butylphenol.

The amount of chain terminators used is from 0.1 to 5 mol% with respect to 1 mol of each diphenol used. The addition of the chain terminator may be carried out before, during or after phosgenation.

Optionally, branching may also be added to the reactants. Preferred branching agents are at least trifunctional compounds known from polycarbonate chemistry, in particular those having at least 3 phenolic OH groups.

Branching agents also include, for example, phloroglucin, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -hept-2-ene, 4,6-dimethyl-2,4 , 6-Tri- (4-hydroxyphenyl) -heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzene, 1,1,1-tri- (4-hydroxyphenyl) -ethane , Tri- (4-hydroxyphenyl) -phenylmethane, 2,2-bis- [4,4-bis- (4-hydroxyphenyl) -cyclohexyl] -propane, 2,4-bis- (4- Hydroxyphenyl-isopropyl) -phenol, 2,6-bis- (2-hydroxy-5'-methyl-benzyl) -4-methylphenol, 2- (4-hydroxyphenyl) -2- (2, 4-dihydroxyphenyl) -propane, hexa- (4- (4-hydroxyphenyl-isopropyl) -phenyl) -orthoterephthalic acid ester, tetra- (4-hydroxyphenyl) -methane, tetra- (4 -(4-hydroxyphenyl-isopropyl) -phenoxy) -methane and 1,4-bis- (4 ', 4 "-dihydroxytriphenyl) -methyl) -benzene and also 2,4-dihydrate Hydroxybenzoic acid, trimesic acid, cyanuric chloride and 3,3-bis- (3-methyl-4-hydroxyphenyl) -2-oxo-2,3-dihydrate Roindole is preferred.

The amount of branching agent optionally used is 0.05 to 2 mol% relative to 1 mol of each diphenol used.

Branching agents can be initially introduced with the diphenols and the chain terminators into the aqueous alkali phase or added prior to phosgenation as a solution in an organic solvent.

Some of the carbonate groups in the polycarbonates, such as up to 80 mol%, preferably 20 to 50 mol%, can be replaced by aromatic dicarboxylic acid ester groups.

The polycarbonates according to the invention may be homopolycarbonates or copolycarbonates, and mixtures thereof. The polycarbonates according to the invention can be aromatic polyester carbonates, or polycarbonates present in a mixture with aromatic polyester carbonates. The term polycarbonate typically refers to a polycarbonate substrate obtainable according to the process of the invention.

The polycarbonates of the invention have a relative viscosity at an average molecular weight M _w of 12,000 to 400,000, preferably 23,000 to 80,000, in particular 24,000 to 40,000, at a concentration of 0.5 g of polycarbonate per 100 ml of dichloromethane at 25 ° C. in dichloromethane. Measured and determined).

The molded articles according to the invention made from the high purity polycarbonate substrates according to the invention are in particular automotive windowpanes and headlight diffusers for automotive reflectors which have no defects in the molded articles and are highly important. The molded article is produced by injection molding, extrusion and extrusion blow molding processes using the polycarbonate according to the invention having an appropriate molecular weight.

Molded articles and films according to the invention are characterized by very low defect rates in the film laser scan test and very low haze of less than 0.5%, in particular 0.4%, in turbidity measurements. Molded articles according to the invention have defects per m ² of less than 300, in particular less than 250, preferably less than 150, measured on an extruded film of 200 μm.

The following examples illustrate the invention. The present invention is not limited to these examples.

To prepare the polycarbonate, 1,1-bis (4-hydroxylate phenyl) -3,3-dimethyl-5-methylcyclohexanone (residual oxygen is introduced in the stirring tank five times and then introduced nitrogen five times. Sodium bisphenolate / disodium 1,1-bis- (4-hydroxyphenyl) -3,3-dimethyl-5-methylcyclohexanone solution (57 mol%: 43) Mol%) and sodium hydroxide solution were dissolved with the exclusion of oxygen and mixed with a solution of BPA (BPA in continuous contact with sodium hydroxide solution as a melt) in sodium hydroxide solution. The sodium hydroxide solution used had different concentrations and purity (see Table 1), and the initial sodium hydroxide solution was further diluted with a 6.5% concentration of sodium hydroxide solution to dissolve the bisphenol. The sodium bisphenolate solution was filtered through a 0.6 μa filter and used for the polycarbonate reaction. After the reaction, the reaction solution was filtered through a 1.0 μnom bag filter and fed to the washing process. Here, the mixture was washed with 0.6% hydrochloric acid and then further washed five times with filtered deionized water. The organic solution was separated off from the aqueous solution and the organic solution was heated to 55 ° C., then filtered first with a 0.6 μa filter and then with a 0.2 μa filter. After isolation, poly-1,1-bis- (4-hydroxyphenyl) -3,3-dimethyl-5-methylcyclohexanone-co-2,2-bis- (4-hydroxyphenyl) -propane carbonate Obtained. The polycarbonate obtained had an average molecular weight M _w of 31,000.

Characteristics of Sodium Hydroxide Solution One 2 3 % NaOH 50 50 32 Fe (ppm) 0.7 0.46 0.02 Ca (ppm) 2.0 0.4 <0.1 Mg (ppm) 0.5 0.2 <0.1 Ni (ppm) 0.2 0.2 <0.01 Cr (ppm) 0.4 0.25 <0.01 Zn (ppm) 0.1 0.05 0.06 Total (ppm) 3.9 1.56 <0.3 Concentration in 100% NaOH One 2 3 Fe (ppm) 1.4 0.9 0.06 Ca (ppm) 4.0 0.8 <0.3 Mg (ppm) 1.0 0.4 <0.3 Ni (ppm) 0.4 0.4 <0.03 Cr (ppm) 0.8 0.5 <0.03 Zn (ppm) 0.2 0.1 0.19 Total (ppm) 7.8 3.0 <0.9

The service life of the filter for various filter positions is in each case as follows.

Experiment number for which sodium hydroxide was prepared Filter service life One 2 3 0.6 μa filter before reaction 12 h 10 d 30 d After reaction 1.0 μa filter 24 h 30 d > 60 d Final filter 1 = 0.6 μa filter Final filter 2 = 0.2 μa filter 12 h 3 d 21 d

Films were extruded into polycarbonates prepared with sodium hydroxide solutions from Experiment Nos. 1 to 3, and they were subjected to a film laser scan test using known methods. The extruded film was 200 μm thick and 60 mm wide. A He / Ne laser (having a “point diameter” of 0.1 mm) scanned the film in the width direction at a scan frequency of 5000 Hz and scanned at a feed rate of 5 m / s in the length direction. In this way, all defects (more than 0.10 mm in diameter) that cause scattering of the transmitted laser beam are detected in the photomultiplier and counted using software. The number of visible defects per kilogram of polycarbonate or per m ² of film is a measure of the surface quality of the film and the purity of the polycarbonate.

Evaluation of Extruded Film by Laser Scanner Experiment No. of Sodium Hydroxide Solution Prepared PC Number per m ^{2 of} surface One 2 3 0.10 to 0.30 mm 194 99 53 > 0.30 mm 216 128 72 gun 410 227 125

Solid sheets for automobile windshields and headlamps were prepared from polycarbonates prepared with sodium hydroxide solutions from Experiment Nos. Polycarbonates prepared with Sodium Hydroxide solution of Experiment No. 3 had a small percentage of flash and high luminous efficiency.

Color sample flakes were made from polycarbonates of different properties. This color sample flakes had different haze according to ASTM D1003. Color sample flakes (thickness 4 mm) made with sodium hydroxide solution from Experiment No. 3 have a particularly low haze of 0.4%, resulting in less diffuse light scattering when used as a window / headlight diffuser.

Claims (8)

A polycarbonate substrate prepared on the basis of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone having less than 300 defects per m ² as measured by a 200 μm extruded film. A polycarbonate substrate prepared on the basis of 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone having less than 250 defects per m ² as measured by a 200 μm extruded film. Use of the polycarbonate substrate of claim 1 for producing a polycarbonate molded article. A process for producing a polycarbonate molded article having a small number of defects, wherein the polycarbonate substrate according to claim 1 is used as a starting substrate. Molded articles made of polycarbonates based on 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone with less than 300 defects per m ² as measured by a 200 μm extruded film . The molded article according to claim 5, wherein the turbidity is less than 0.5%. Based on 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone, having less than 300 defects per m ² as measured by a 200 μm extruded film and having a haze of less than 0.5% Disc made of polycarbonate. Based on 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexanone, having less than 300 defects per m ² as measured by a 200 μm extruded film and having a haze of less than 0.5% Sheet made of polycarbonate.